<!DOCTYPE html>
<head>
  <title>内容超线处理</title>
  <meta http-equiv="content-type"
        content="text/html; charset=UTF-8">
  <style>
    body {
      margin: 5px auto;
      padding: 0px;
      width: 600px;
      border: 1px solid blue;
    }
    .box1 {
      float:left;
      height: 100px;
      width: 150px;
      margin: 5px;
      background-color: burlywood;
      border: 5px solid green;
    }
    .rightfloat {
      /* 右浮动 */
      float: right;
      height: 100px;
      width: 30%;
      margin: 5px;
      background-color: burlywood;
      border: 5px solid green;
    }
  </style>
</head>
<body>
<div class="box1">111</div>
<div class="box1">222</div>
<div class="rightfloat">333</div>
<div style="clear:both"></div>
</body>
</html>